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Seahorses under threat in marine parks: study

MATTHEW KELLY

In decline: A White's Seahorse with its nose bitten off by a predator. Photo: Supplied

The state’s controversial network of marine parks and reserves are inadvertently threatening seahorse populations, new research has found.

While the reserves are widely credited with improving overall marine diversity and abundance, the four-year study found there was also an increase in seahorse predators.

“Our results are contrary to what has previously been suggested. This is one of the reasons why we did this project, to test the effectiveness of no-take marine reserves as a tool for seahorse conservation,” Port Stephens marine scientist David Harasti, who recently completed his PhD through the UTS School of the Environment, said.

"It appears seahorses may end up being on the losing species as a result of increased numbers of predators": Dr David Harasti. Photo: Supplied

Dr Harasti monitored populations of White’s Seahorse, and their predators, such as octopus, flathead and scorpionfish, at four sites around Nelson Bay within the Port Stephens-Great Lakes Marine Park.

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He found the number of seahorses were higher outside the no-take areas, while predator numbers were higher inside the no-take areas.

‘‘When the numbers of predators went up, the numbers of seahorses went down,’’ Dr Harasti said.

Reserves threatening seahorse populations: Predators of the White's Seahorse have followed it into marine conservation parks. Photo: Supplied

‘‘Within marine reserves there will be winners and losers and it appears seahorses may end up being on the losing species as a result of increased numbers of predators following the removal of fishing.’’

Project supervisor and UTS head of the school of the environment, Bill Gladstone, said Dr Harasti’s research would require authorities to reconsider the effects of marine reserves and what conservation measures were needed to protect White’s Seahorse.

The Port Stephens findings are also supported by the team’s earlier research into the habitat preferences of the Sydney seahorse.

Those findings, recently published in the Journal of Fish Biology, recommended a broader approach to seahorse conservation than simply relying on marine reserves.

“We can only conclude that the declaration of a no-take marine reserve by itself may not be the best option for conserving declining seahorse populations,’’ Dr Harasti said.

“We found that seahorses used a variety of habitat types, from sponge gardens to soft corals, and that juveniles prefer different habitats to adults. They also show very strong site fidelity which means they tend not to move very far. In fact, one individual male was observed living in the same sponge for 17 months,’’ he said.

Dr Harasti’s research findings will be published in the science journal PLOS ONE on Wednesday.